246 FLORA INJHCA- island of Cheduba, and if so, the latter is the northern limit of that tree. 7. AVA AND PEGIL The sources of the river Irawadi are, according to the best authorities, between 27° and 28° of norili latitude, and the direction of its valley is nearly due north and south. The mountains in which this immense river takes its rise probably rival in height the Eastern Himalaya, but the meridional ranges which bound its valley on each side do not long re- tain any great elevation, though they are continuously from 4000 to 8000 feet in height almost as far as the sea. The transverse range, which separates the upper part of the west- ern branch of the Irawadi from the valley of Assam, is also of moderate elevation, varying probably between 5000 and 6000 feet. The slope of the valley of the Irawadi is greater than that of the Indus or Granges, if the estimates of elevation given by Griffith may be relied on. The valley of Hukum is stated to be 1000 feet above the level of the sea. The determination however was made by boiling water, which, at such low levels, is too fallacious a test to be depended on. The central branch of the Irawadi, at Manchi in 27a 20* north latitude, where it was visited by Wilcox, has an elevation of 1800 feet*, and runs over a pebbly bed. Its elevation at Bhaumo, in lat. 24°, is estimated by the same authority to be about 500 feet. The valley of the Irawadi is much less open than that of the Ganges, being interrupted in many places by transverse ranges. In the upper part of its course these are numerous, aud the lateral valleys they enclose are comparatively small; but lower down there is a great expanse of level country, though the hills occasionally attain au elevation of 8000 or iOOO feet close to the river. The direction of the monsoon wind in the valley of the Irawadi appear** to be nearly from south to north. The * As, Ites. xvii. 441.